Machine for grinding gear wheels



Sept. 11, AEPPL] MACHINE FOR GRINDING GEAR WHEELS 4 Sheds-Sheet 1 Filed Sept. 10, 1948 Sept. 11, 1951 A. AEPPLI MACHINE FOR GRINDING GEAR WHEELS 4 Sheets-Sheet 2 Filed Sept. 10, '1948 Sept. 11, 1951 ArAEPPLl 2,567,460

MACHINE FOR GRINDING GEAR WHEELS v Filed Sept. 10, 1948 4 Sheets-Sheet -5 4 Sheets$heet 4 A. AEPPLI MACHINE FOR GRINDING GEAR WHEELS Sept. 11, 1951 Filed Sept.

Hag/2 Pate'nteci Sept. H, 1951 UNITED STATES PAT OFFICE I assure i MACHINE Fon GRINDING GEAR WHEELS- Albert Aeppli; Zurich, Switzerland, assignor to Maag-Zahnrader und gesellschaft, Zurich, Switzerland Applicationseptemlier 10, 1948, Seriallflo. 48,554 In Switzerland September 17, 1947 1 present invention relate to a methodof and machine for grinding gear" wheels in accord with the generating process, for the purpose of producing tooth profiles which partially deviate from the'involute form.

As. is known in the art, the teeth meshing at an -one timein highly loaded or'stressed gears are deflected by virtue of. thefhigh tooth pressure which deflections are a maximum at the tooth-face.- Each freshly intermeshing pair of teeth, now, causes a slight impact, sincethe tooth of the driving whee'lowing tothe' deflecti'on of' the preceding tooths'lightly leads with. respectto the appurtenant tooth of the driven wheel and abuts against the face of such latter tooth. In order to eliminate such disadi'r 'antage, the teeth are given a profile which paru'any deviates from the true involute form, i. e. the'tooth' faces or roots are suitably rounded offI.

Methods. and machines serving such purpose are known in the art; In gear wheel grinding machines operating with form discs, the latter are so profiled as to impart'the'desired rounding to the teeth to be ground. Further, in machines grinding in accord with the generating method, the rolling cylinder of the generating means suitably isadapted noncircular, or the. work is additionally moved when grinding the tooth faces or roots.- Since, however, such latter machines usually work different tooth side simultaneously, by means of two grinding wheels, there is the disadvantage that one cannot perform profile changes of any form and size desired, since,v perhaps, one at" the same time has grind the tooth root on the left flank and the tooth face on the right flank. In such case, one

Claims. (Cl. 51 123 -Ma'schinen' Aktientween the cam and deflector, which movement I i linked with that of thegenerating means,

i's forced to work each toothside per se, thus doubling the time of grinding.

Such disadvantage is eliminated, by the method disclosed in my present invention, in that the two grindin wheels, instead of the work piece; intermittently are subject to an additional movement, thus also producing tooth profiles which partially deviate from the'involute form. In this manner, it" is possible to displace each grinding wheel per se, at a predetermined time, by anamount' corresponding to the amount of rounding or transition at the tooth face or root. It, the'refore', is possible to simultaneously "grind two diifere'nt tooth sides by means of two grinding wheels. Such displacement of the latter may ,be brought about by any suitable means which are known per se.

1 In the machine for carrying out the method of. my present invention, the grindin wheels are displaced through cams which act onto dc- 'fiectors; a relative movement being set" up 'be- The method and various embodiments of the machine according to my present invention are illustrated in the accompanyin drawings in which: I r p v Fig. 1 schematically shows an involute tooth profile partially deviating from the- 'involute form;

Fig. 2 the same pro-file'enlarged, Q l

Fig. 3 a schematic representation of the tooth profile, including the grinding wheel, cam and deflecting roller for the intermittent displace-- ment of the grinding wheel,

Figs. 4 and 5 show a gear grindingmachine working by means of two grinding wheels ac? cording to the such method, in elevation and plan respectively, I

Fig. 6 shows-a partial view of the said machine, including the generating; means,

Fig. 7 a side view of Figs; 4 and 5,

Fig. 8 one form of the means" for displacing the grinding wheels, V

Fig. 9 another form for displacing the grinding wheel carrier in direction of the generating plane, i

Fig. 10 the same means,v but for displacing the grinding wheel in direction of its axis ofrotaf tion and parallel to the line of engagement, and

Figs. 11 and 12 show an elevation, partly in section, and a plan view of a gear grinding machine in which the two grinding wheels perform the generating movements, while the gear wheel only performs a feed motion relative to the grinding wheels. 7

Fig. 1 shows" a general involute tooth profile 2'-4, including the base circle do, the pitch circle d and the addendum circle do. On the tooth face, a deviation from the involute may be seen, beginning at point I and extending to the addendum circle at 2. Such deviation involves the angle (pi on the base circle; Simi# larly, a deviation or transition is provided on the tooth root, extending between the points 3 and 4 and subtending the angle (p2. Fig. 2 shows the same profile enlarged, the deviation on the tooth face or addendum in direction of the addendum circle and in direction of the line of engagement F being designated by b and a respectively; The said two deviations are so adapted as to smoothly pass into the involute curve at the points I and 3.

The said profile changes or deviations are brought about by a corresponding displacement of the grinding wheel.

One form of such means is schematically Shown in Fig.3, operating through a cam 5 secured to a carrier '6' which follows the rotation of the shaft 9 of the gear 8 to be ground, relative to the stationary grinding wheel I, for the purpose of producing the generating motion. By virtue of such rotation, the cam on passing through the angle (121 from point Ia to 2a, displaces a deflector In by the amount e which, reduced accordingly, is transmitted onto the grinding wheel I. The latter successively approaches the tooth profile, from point I to 2 thereof, in direction of the grinding wheel axis, i. e. parallel to the line of engagement F, by the amount a (Fig. 2), whereby the tooth face is rounded as desired.

In Figs. 4-8 there is shown a gear grinding machine operating in accord with the method set forth above. A carriage I2 is mounted dis-. pla-ceable on the bed H and carries a further slide [3. On the latter is mounted a shaft 8 supporting the gear wheel 8 to be ground, which shaft is connected through the indexing means l4, l5 to the hobbing elements. The latter comprise the rolling cylinder l6 (Fig. 6) to which steel tapes ll are secured. The ends of the latter are secured to the stirrup I8 which is attached to the carriage l2. When the slide 3 moved transversely of the carriage |2, the

and root on one and the same tooth flank may be rounded off by providing two rises e on the cam periphery.

In the form of invention described above, the deviation of the tooth profile from the involute or, respectively, the grinding wheel feed is equal to the rise e. Since the values involved are very cylinder I6 rolls off on the stretched tapes I! and thus imparts the necessary generating movement to the gear wheel 8 relative to the grinding wheels I.

A crank gear l9 serves for producing the transverse movement of the slide l3, and is actuated by The a suspended from a horizontally displaceable slide 29 by means of two resilient hangers 28. The said slide 29 in its turn rests on the slide 30 which is vertically adjustable on the upper portion of the bed II. A spring 3| so abuts against one of the hangers 28 as-to force the deflecting roller I0 against the cam 26.

A similar driving arrangement also is associated with the other grinding wheel I. The drive is derived from the shaft 23 through a pair of bevel gear wheels 32, 33 and the shaft 34 onto a further pair of bevel gear wheels 35, 36. The latter drive the cam 26 through the left-side pair of gear wheels 24, 25.

The machine operates as follows: The gear ratio of the wheels 2|, 22 and 24, 25 is so chosen that the cams 26 perform a revolution in the same time as the crank l9. It is required to round off the tooth faces of the wheel 8. In the form of machine described, grinding wheels I are used, of which the plane grinding faces are put opposite each other and at right angles to the hobbing tapes ll. The machine, therefore, grinds with a pressure angle of 0 relative to the vertical. A rounding of the tooth profile is produced on feeding the grinding wheels toward the centre .of the machine. It is from this reason that each cam 26 (Fig. 5) is given a rise 6 of which the magnitude and run correspond with the desired degree of rounding off. As each revolution of the cam corresponds to a double generating movement of the gear wheel 8, the position of the rise 6 on the cam periphery may be accurately ascertained. Further, also the tooth face small, in the order of a few hundredths of a millimetre, it would be more advantageous to make the curve e to a larger scale, as shown in Figs. 9 and 10. In this case, the plane working faces of the grinding wheels I are facing outwardly and form the pressure angle a with the vertical. For the purpose of rounding the tooth profile, the grinding wheels, therefore, have to be outwardly displaced. Such displacement is brought about, according to Fig. 9, by adjusting the slide 31. The cam disc 26- is pinned to a shaft 38 which in its turn is So rotated through the crank-gear shaft 20 (Fig. 5) as to perform a revolution'therewith. A transfer lever 39 comprises an idling roller 40 at one, end, while the shorter arm contacts a stop of the grinding-wheel slide 31 which is forced against the lever 39 through a spring 4|. The said roller 40, therefore, continuously contacts the said cam disc 26'. The curve of the latter, in the present case a depression e, is derived as to form and position from the desired profile rounding. Since the slide is displaced parallel to the straight generating line G on the pitch circle (1, the magnitude of such displacement on the addendum circle da (Fig. 2) is b, the ratio e b defining the length of the lever arms.

The arrangement shown in Fig. 10 is similar to that shown in Fig. 9, but in this case the grinding wheel is displaced in direction of the line of engagement or contact F by the amount a (Fig. 2). To such end, the grinding-spindle sleeve 42 is displaced in direction of its axis, in that a spring 4| presses an abutment 43 which is rigidly secured to the said sleeve 42, against the shorter arm of the lever 39. The idling roller 4|) of. the latter is deflected through the cam disc 26'.

While, heretofore, the work has been subject to the generatin movement and the feeding movement relative to the grinding wheels, Figs. 11 and 12 show a machine in which the gear wheel to be ground solely performs the feeding movement, and the grinding wheels perform the entire generating movement and, further, an intermittent displacement for rounding off the tooth profile. The grinding-wheel carrier 44 is secured to a slide 45 resting on ball races 46 of a segment-like saddle 41 which is rotatable about the wheel axis C. The stationar rollin cylinder I6 secured to the standard I and provided with the steel tapes II, also is arranged centrically to the said axis C. The free ends of the said tapes are screw-connected to two tensing levers 48, 48 which are so interconnected through a tie-rod 48 as to subject the tapes to a tensile stress. The said lever 48 is provided with a third lever arm havin an idling roller 50 which rolls off a guide plate 5| under the action of a spring 53. The said plate 5| comprises a plane face and a curved portion 52. A rack driven by means of the piston of a pressure-oil cylinder 54, causes the saddles 41 to swing or swivel. Gears 56 mesh with the rack 55. and are operatively connected to gears 51 which actuate toothed segments 58 secured to the saddles 41. The shaft 8, on which the gear 8 is mounted, is mounted on a saddle 59. The gear 8 does not participate in the hobbing movement, but is axially fed, in that the saddle 58 is displaced on the standard I I through the rigging i0 which is actuated through a crank-gear 6i driven by the motor 62.

By virtue of the swiveling or swinging movement of the two saddles 41 about the axis C, the tensed steel bands I! are caused to roll off the stationary rolling cylinder I6, and the plane outwardly directed working faces of the grinding wheels 1 move tangentially with respect to the involute-shaped tooth profile. Here also the tooth face or addendum shall be rounded 01f. During the generating movement, the idlin roller 50 (Fig. 12) rolls along the guide and arrives, at one end of the latter, on the curved portion 52. The roller 59, thus, is displaced somewhat, upon which the lever 48 is rotated clockwise through a small angle. Since the lever 48 is connected to th steel tapes I! secured to the stationary rolling cylinder 16, its rotation causes a displacement of the slide 45 and, therefore, of the grinding wheel I, which displacement corresponds to the desired rounding of the tooth face as to magnitude and run. A similar arrangement for displacement also is associated with the other grinding wheel so that the profiles of both tooth flanks may be simultaneousl provided with any desired deviations from the true form of involute.

Although as exemplification of the invention the grinding of spur gear wheels of the ordinary type has been chosen it is obvious that the method is not limited to that particular type of wheel alone, but may be applied to other known types. Consequently, the claims are not intended to be limited to the grinding of any specific type of gear, except where the prior art requires it.

What I claim as new and desire to secure by Letters Patent is:

1. In a gear grinding machine for producing the tooth-profile on the work by means of relative rolling motion between the work and the grinding tool, two grinding wheels, a work carrier, work carrier drive elements, means for generating a normal involute motion relative to the grinding wheels and applying said motion to said work carrier drive elements, deflector means operatively connected to the grinding wheels for intermittently displacing the grinding wheels in the direction of the straight rolling ofi line, and cam discs acting on the deflector means and performing one revolution for each double passage of the rolling distance of the generating means so as to produce tooth profiles partially deviating from the involute shape.

2. In a gear grinding machine for producing the tooth-profile on the work by means of relative rolling motion between the work and the grinding tool, two grinding wheels, a work carrier, work carrier drive elements, means for generating anormal involute motion relative to the grinding wheels and applying said motion to said work carrier drive elements, slides carrying the grinding wheels, for intermittently displacing these wheels, and cam discs acting on the slides for displacing these slides in direction of the straight rolling off line and performing one revolution for each double passage of the rolling distance of the generating means so as to produce tooth profiles partially deviating from the involute shape.

3. In a gear grinding machine for producing the tooth-profile on the work by means of relative rolling motion between the work and the grinding tool, two grinding wheels, a work carrier, work carrier drive elements, means for generating a normal involute motion relative to the grinding wheels and applying said motion to said work carrier drive elements, grinding wheel carriers for intermittently displacing the grinding wheels, and cam discs acting on the grinding wheel carriers for displacing these carriers in the direction of the spindle axis and parallel to the line of engagement and performing one revolution for each double passage of the rolling distance of the generating means so as to produce tooth profiles partially deviating from the involute shape.

4. In a gear grinding machine for producing the tooth-profile on the Work by means of relative rolling motion between the work and the grinding tool, two grinding wheels, a work carrier, work carrier drive elements, means for generating a normal involute motion relative to the grinding wheels and applying said motion to said work carrier drive elements, cam discs performing one revolution for each double passage of the rolling distance of the generating means, cams on the cam discs of a rise greater than the grinding-wheel displacement, and transmitting means intermediate of cam and grinding wheel, and adapted to reduce the deflection originating from the cam to the magnitude of the actual displacement and carry same forward onto the grinding wheel so as to produce tooth profiles partially deviating from the involute shape.

5. In a gear grinding machine for producing the tooth-profile on the work by means of relative rolling motion between the work and the grinding tool, two grinding Wheels, a work carrier, work carrier drive elements, means for generating a normal involute motion relative to the grinding wheels and applying said motion to the grinding wheels, said generating means including a stationary rolling cylinder and steel tapes secured to this cylinder, slides for carrying the grinding wheels, two tensing levers mounted on each slide and connected to the steel tapes and to each other, a deflector correlated to one of the said tensing levers, and a cam for acting on the deflector for displacing it, which displacement of the said deflector gives rise to a partial rotation of the said tensing levers, whereby the slide including the grinding wheel undergoes a displacement in direction of the steel tapes by an amount defined by the rise of the cam, such rise corresponding to the desired profile rounding or profile transition.

ALBERT AEPPLI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,183,020 Maag May 16, 1916 2,164,978 Wildhaber July 4, 1939 2,325,836 Drummond Aug. 3, 1943 2,392,819 Gruenberg et a1. Jan. 15, 1946 2,404,573 Graf July 23, 1946 FOREIGN PATENTS Number Country Date 403,886 Great Britain Jan. 4, 1934 

